ffmpeg - compiling an example file

I wanted to compile a file from the ffmpeg examples directory, since I'm considering writing golang that links directly to ffmpeg via cgo.

I don't use C often enough to remember how everything works, so I have to re-figure-out how to compile stuff every time. Here's what I ended up with:

clang \
  -I/opt/homebrew/Cellar/ffmpeg/7.0.2/include \
  -L/opt/homebrew/Cellar/ffmpeg/7.0.2/lib/ \
  -lavutil -lavfilter -lavformat \
  decode_filter_video.c

• -I: tells clang to search the given directory for header files
  • You can use the C_INCLUDE_PATH environment variable instead if you prefer
  • homebrew puts all its include files in /opt/homebrew/include, so if you want to be more general you can add that to C_INCLUDE_PATH in your shell initialization, or use that as the -I argument
• -L: tells clang to search the given directory for objects to link
  • You can use the LIBRARY_PATH environment variable instead
    • The difference between LIBRARY_PATH and LD_LIBRARY_PATH is that the latter is used at runtime for loading dynamic libraries
• -l<libname>: tells clang to link the library given by <libname>
  • I had to just kind of guess at which ones of these I needed to resolve all the undefined symbols errors I was getting
  • Is there a way to have the computer figure out which libraries you need, or is it just required for the programmer to know which -l<whatever> flags need to be included?

clangd

Without any configuration, clangd won't be able to find the header files you need. Here's a config file I created to give it the header directory and add -Wall. Save it to .clangd:

CompileFlags:
  Add:
    - "-Wall"
    - "-I/opt/homebrew/Cellar/ffmpeg/7.0.2/include"